Video technology news, reviews and opinions

January 11, 2006

What's 24p?

The new generation of HDV cameras has started a big debate regarding the definition of 24p. Here's the deal.

First off, what does 24p mean? 24 frames per second (like a motion picture), progressive frames. This means, unlike normal NTSC video which samples half a frame (called a field, consisting of every other line of a frame) every 60th of a second, a whole frame is sampled every 24th of a second. The idea is to get a look on video that approximates the traditional cinematic feel.

So, what's the right way to do it? In an ideal world, we'd have a CCD or CMOS chip in the camera capable of sampling a whole frame at a time, recording to a tape format that recorded 24 individual frames each second. It's not an ideal world though, is it?

In the prosumer space, the first camera to make big waves in this area was the Panasonic DVX-100. It owes much of its success to the fact that it actually did the 24p thing right. It used progressive CCDs so that it could capture 24 individual frames. It then gave you the option of two different well-documented pulldown patterns for putting those 24 frames into the 60 fields of NTSC video. It was straightforward, it was reversible, and it looked darn good.

What the hell went wrong?

HDV has introduced a number of new problems. First off, the highest resolution within mainstream HD (the stuff that gets broadcast) is 1080i, an interlaced format running at 60 fields per second, just like standard definition. The first round of real HDV cameras, the Sony FX1 and Z1U, were optimized for this resolution. Due to this, their CCDs were designed for interlaced recording. Sensing that there was a demand for 24p recording, Sony added a "CineFrame" setting, which attempts to give a "film look" by deinterlacing the footage and tossing out some fields to get a 24 frame per second rate. For reasons I don't fully understand though, Sony chose a very odd cadence, or timing pattern. This gives motion shot in the CineFrame mode a very unrealistic look. The footage than goes through a pulldown to fit it into a traditional 60i form, but because of their odd cadence, this isn't easily reversable. Getting a true 24p timeline from footage shot on the Sony would be quite a bit of work. Frankly, it's all but unacceptable to anyone but the Soccer Mom videographer.

Hoping to capitalize on the frustration the Sony settings caused, JVC released the GY-HD100 at NAB last year. You can learn more about my feelings towards this camera in a previous post, but needless to say, it doesn't thrill me. However, if all you need is progressive video at 24fps, and you can deal with a camera that's using a bit of an odd spec, it might be the camera for you. Unfortunately, the best you're going to do is 720p24, not a full 1080p24. This is a pretty significant resolution drop.

The Panasonic HVX-200 attempts to pick up where the DVX-100 left off. You get very similar options for recording 24p, and because it's using DVCProHD on a p2 card, you can get native 24p files. The only downside is that the Panasonic CCDs may not be quite as high resolution as one might hope. Judging from the footage coming off of it though, it's still a beautiful camera.

Canon goes a route similar to Sony with their XL-H1, but with some key differences. They're still using a 1080i CCD, so you won't get native progressive frames. However, when doing 24p recording, the Canon clocks the ccds at 48hz, so that they're capturing 48 distinct moments in time. Then, using some fancy deinterlacing algorithms, they blend fields to make 24 discreet frames. While this does cost some clarity and resolution, you at least avoid the cadence issues of the Sony. Canon also uses what they call a "24f" recording format, that puts 24fps on tape, instead of using a pulldown to get to 60i. Unfortunately, this means that they've introduced yet another format that won't work with other HDV devices. Fun!

So, if you want to shoot absolute, "true" 24p, you need an HD100 or HVX200. If you want to shoot "nearly true" 24p, get the Canon. And if you want to shoot "not really 24p at all", get the Sony. At this point, if you need to edit your video in Final Cut Pro, you're pretty much stuck with the Sony or the Panasonic.

Comments

Hi- I found your post when I searched for 24P definition. I'm considering the Canon XL2, and I use Final Cut Pro. Can you explain to me why you say "you're pretty much stuck with the Sony or the Panasonic"?

The reason that I wrote that you're "stuck with the Sony of the Panasonic" is that, when I wrote that post, Final Cut wouldn't really deal with footage off the JVC HD100 or the XL-H1. It's slightly better at the XL-H1 now, and HD100 support is still lacking.

However, all of that only pertains to HD footage. Since you're talking about the XL2, you're working with Standard Def, in which case Final Cut Pro will work great. It can support both the 60i and 24p footage off the XL2 with no problem. I have a number of students shooting with that camera and they have no troubles.

Hi, I hope your still responding? With the new Final Cut Pro Studio 2 out, will that support the JVC HD100? And, is there a better cammera now than the JVCHD100?

Thanks.

Posted by: KEITH at October 9, 2007 9:05 AM

FCP2 definitely supports the JVC. The HD100 has been pretty well replaced by the 110/200/250. They're pretty sweet cams for the price. I think it'd have to be a personal decision based on form factor and whether you need long recording times (IE, tape) versus short-but-easily-ingested clips (IE, panasonic p2).

Posted by: Colin McFadden at October 9, 2007 9:09 AM

Thanks for this article! It was exactly what I was looking for. By reading it I noticed you're a teacher on this field? May I ask a couple of questions based on your experience?
1.Checking cameras that support real 24p I ran into the Sony HVR-V1U 1080i HDV Camcorder. Is this one still in your "sony/panasonic stuck list"?

2.Which camera would you recommend for shooting videoclips? And which format? (4:3 or 16:9)

regards,
Alvaro

Posted by: afecelis at March 18, 2008 5:05 PM

Thanks for this article! It was exactly what I was looking for. By reading it I noticed you're a teacher on this field? May I ask a couple of questions based on your experience?
1.Checking cameras that support real 24p I ran into the Sony HVR-V1U 1080i HDV Camcorder. Is this one still in your "sony/panasonic stuck list"?

2.Which camera would you recommend for shooting videoclips? And which format? (4:3 or 16:9)